It is important that an annular, lipped seal or lip seal be fitted centrally in the gap to be sealed, with the support for the external circumference of the seal being properly centered relative to the shaft centerline. The function of the lip seal will be lost or negatively affected if the gap is wider on one side than the other. In U.S. Pat. Nos. 5,013,050 and 5,052,695, assigned to Ford Motor Company, tools for supporting and installing a lip seal in a gap in a device, such as an oil seal around a rotating shaft, are disclosed where the interior, lip portion of the seal is flexed into a retracted state about an axially extending cylindrical surface, or sleeve, connected to an outer plate which extends radially outward of the seal. The radially extending outer plate of the tool is particularly adapted to engage with the end plate or housing body of the machine to act as a centering guide upon axial insertion of the retracted lip seal into the gap between the shaft and the stationary casing or body of the machine. The seal is assembled into the gap by interference fit with the inner diameter of the machine's shaft housing. With the seal thus being installed about the shaft, the tool is axially withdrawn, causing the interior lip to flex radially inward into engagement with the shaft. The tool, which may be made of plastic, may then be discarded.
In operation, lip seals have a limited useful life due to wear. At the end of the useful life, leakage will develop at the interface between the stationary lip seal and the reciprocating/rotating shaft. When leakage is observed, the operation of the fluid handling machine generally must be terminated and the machine at least partially dismantled to remove the previous lip seal for purposes of replacement. There is the possibility that a significant cost in operating downtime may be suffered due to the replacement of the lip seal.
Various approaches have been undertaken to improve the performance and/or to lengthen service periods between required maintenance. Thus, for example, U.S. Pat. No. 2,836,441 to Doble discloses a shaft seal system in which the shaft includes a conical surface and the seal is axially repositionable along the shaft to improve engagement between the seal and the shaft as the seal experiences wear. U.S. Pat. No. 3,773,336 to Walter discloses a seal system in which a spare seal member is initially positioned adjacent a recess in the shaft (or associated bushing), thereby avoiding engagement with the shaft until needed. The spare seal member may be brought into contact with the shaft by axially repositioning the seal holder or the shaft/bushing. U.S. Pat. Nos. 5,820,132 and 6,152,454 to Marnot also describe seal systems in which a spare seal is initially positioned adjacent a set back region formed in the shaft. As the spare seal is axially repositioned so as to be brought into engagement with the shaft, the replaced seal is moved adjacent a set back region formed in the shaft, i.e., out of engagement with the shaft.
The inventor has devised a more economical sleeve-type system for the simplified, yet reliable, installation of a lip seal or seals into the gap about a shaft to enable the shaft to be sealed during operation of the machine. Additionally, the inventor has devised a back-up or spare seal capability to extend useful wear life of the sealing operation.